


Incendio

by moonside



Category: Final Fantasy XV
Genre: 30!Noctis, 30dk, Alternate Universe - Harry Potter Setting, Alternate Universe - Student/Teacher, BUT ALSO PROMPTO IS UNDERAGE, Frottage, Hufflepuff Prompto, M/M, Poor Noctis, Professor Noctis, Promptis - Freeform, SO PLEASE READ THE TAGS, Sex Toys, Teen!Prompto, only slightly inappropriate use of magic, prompto is an absolute menace
Language: English
Status: Completed
Published: 2018-09-16
Updated: 2018-09-16
Packaged: 2019-07-12 21:11:44
Rating: Explicit
Warnings: Underage
Chapters: 1
Words: 3,443
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/16003385
Author URL: https://archiveofourown.org/users/moonside/pseuds/moonside
Summary: Noctis Lucis Caelum, Hogwarts potions professor extraordinaire, tries to resist his favourite student. With very little success.





	Incendio

**Author's Note:**

> PLEASE READ THE TAGS LMAO.
> 
> This is my Harry Potter AU from hell that my friends and i have been sitting on for months now and it is time to share some with the world. 
> 
> i shouldn't have to disclaim this i s2g but i am well aware that this is gross, pls keep in mind that i'm well aware this is fiction and i do not condone any of this underage age gap crap IRL but. HEY, IT'S FANFIC AND I'M GONNA HAVE FUN WITH THIS.
> 
> also, happy fucking birthday elise, you whore, this is your fault. <3 <3

Prompto Argentum is an absolute _menace._

 

Noctis had no idea, when he’d met the boy all those years ago - and god, how has it been what, _five_ damn years now?! - just the impact it was going to have on his life. He’d had no right in befriending the boy, perhaps; though, at the time, his intentions had been innocent. Noctis has always been a bit of a lost soul, and he’d found his purpose in guiding the young boy--and, of course, he’d sensed a kindred spirit.

 

It’d be _fine._ They’d become fast friends, their mentorship turning warm, affectionate, the boundaries blurring. And then puberty had hit, and _oh,_ it’s been a nightmare ever since.

 

Noctis has been good.

 

He doesn’t _want_ to be good. He wants to drag the kid back to his office, lock the door, flip him over his desk, and fuck him into oblivion. He wants to leave hickeys all over that sun-kissed, gorgeous freckled skin, and he wants his fingers to leave imprints over the jut of hipbone, along those soft, plush inner thighs that still carry just a hint of the boy’s former weight.

 

Fuck, Noctis wants it badly.

 

(He feels awful; sometimes he counts down the days until Prompto’s graduation, until he can finally _have_ him--but at the same time, he’s dreading it, because then Prompto will leave, and this has to just be a teenage whim of the boy’s, right? Noctis doesn’t _know_ what he’ll do when Prompto graduates.)

 

Right now, though, Noct’s pressing the heel of his palm firmly into his forehead.

 

It’s late, later than _any_ student should be up. So, naturally, Prompto’s owl had squeezed her way through the partially open window of his office, carrying a tightly-wrapped, wax-sealed scroll. Noctis _knows_ that when Prompto sends him lettters, it’s never good news.

 

_I’m coming to see you. Playing with my favourite toy~_

 

That’s all the message had read, and Noctis had quickly scribbled out a, _students shouldn’t be out of bed, brat,_ fastened the scroll back to the owl’s leg, and promptly faceplanted into the desk, because he _knows_ Prompto won’t listen. Noct had essentially permanently lent Prompto his cloak a couple of years ago, and he’s been regretting that decision ever since.

 

His dick, of course, doesn’t seem to care about all the details (underage, breaking a million rules, Noctis is a damn _professor)_ because it’s pressing against the seam of his trousers anyway. He’s fucked.

 

A few minutes tick away in silence, Noctis _trying_ to pretend that he’s actually bothering to grade a few essays (he’s barely reading them, always a lenient marker), when the door cracks open. Prompto never bothers to knock anymore; why would he? The damn brat knows he’s _always_ welcome.

 

Noct’s used, by now, to lifting his eyes and seeing nothing except the door silently moving on its own. It cracks open just enough for Prompto’s slender (and invisible) form to slip through, then closes just as silently. The lock clicks - a precaution, as always - and Noctis mumbles a spell under his breath anyway. _Just to be sure._

 

“Hiya, Noct,” Prompto practically _purrs,_ as the cloak slides off, pooling in a slinky, fluid mess on the floor. His hair’s slightly mussed, unkempt and ruffled, and his eyes are bright. He’s wearing joggers and a long, well-worn sweater, the sleeves rolled up to his elbows, the thin band of green around the slightly fraying betraying exactly who it used to belong to. Noct’s eyes narrow in approval; he can’t help it. There’s always a little swell of _possessive_ instinct that kicks in around Prompto, and that only makes his problem that much worse.

 

“You shouldn’t be sneaking out, y’know,” Noctis replies casually. He sets his quill down, though, nudging the stack of parchment to the side. They both know damn well that Noctis isn’t going to get _any_ more work done tonight.

 

“Shouldn’t have given me the cloak, then,” Prompto shoots back, with a smug little smile on his face.

 

“Gonna take it back one of these days,” Noctis agrees. They both know he won’t. Speaking of, though, Noctis lets his gaze shift, pointedly nodding at the silvery pile of Invisibility Cloak on the floor. “... you better take care of it while it’s yours, though. Don’t just leave it there.”

 

Prompto rolls his eyes, but his smirk is wicked. They both know Noctis gives exactly _zero_ fucks about keeping his office tidy. The boy shifts, hips tilting to the side, ass wiggling ever so slightly, as he makes a show of leaning down to gather up the sheer fabric. A quiet _moan_ escapes the boy’s lips, as he moves, and _oh,_ that’s when Noctis remembers the note.

 

That _brat._ That clever, perfect, absolutely _slutty_ brat.

 

“Better?” Prompto asks, as he straightens. His cheeks are slightly flushed, making the freckles stand out stark. His lips are slightly parted, just a bit glistening from a tongue that darts out to wet them. Noctis knows the boy better than he wants to admit, and he can see the tension he’s carrying at the base of his spine, the way his feet are shuffling just a little, bouncing his weight on the balls of his feet, even as he’s _trying_ not to move too much--

 

It’s unfair, how fucking _gorgeous_ Prompto is. Noctis has never really stood a chance resisting him, has he?

 

“Don’t tell me you walked all the way here like this,” Noctis states in response, though they both know the answer. Prompto’s lips quirk up into a playful little smile, and he takes a step forward. He’s biting back a gasp, Noctis knows-- and, imagining Prompto trying to stay _quiet_ as he makes his way through the massive, eerily silent castle, late at night, hidden under the cloak…

 

His cock’s achingly hard against the front of his pants by now, damnit.

 

“Sure did, Noct,” Prompto grins. His hips wiggle a little more, emphasizing just how _wide_ they are, how perfectly tapered his little waist is, even half-hidden in Noct’s old, oversized sweater. It’s gotta feel good, too, because this time, the moan that he lets out is just a bit louder. “Wanted to -- _ah --_ show you…”

 

Prompto stops in front of his desk, and his eyes are dancing with an absolutely wicked fire. They’ve always had such a _connection,_ from the moment they’d met, all those years ago. Back then, it’d simply been a magnetic draw, Noct’s protective instinct clawing its way to the surface of his consciousness, filling a void that he hadn’t even fully realized had existed. The _attraction_ between them, though, it’s gotten stronger, become unbearable, and the love between them, it only complicates things, makes it both better and worse.

 

Noctis wishes he could take a step back, that he could stop this before Prompto regrets it. Before Prompto grows up and regrets _him,_ but damnit, Noctis loves him too much to break his heart.

 

“You’re _thinking_ again,” Prompto accuses him, one hand on his hip, and that fire is burning even stronger in his bright eyes. Noctis shakes his head, laughing a quiet, nearly inaudible huff of laughter, and rolls his eyes. The kid _knows_ him too damn well.

 

“Yeah, I am,” he admits. “So if you’re _trying_ to distract me, better get on with it.”

 

They play this game of back-and-forth often enough. It doesn’t take Noctis by surprise anymore when Prompto dives in head first, when he absolutely overwhelms himself and simply _takes._ So, when Prompto closes the final distance between them, side-stepping around his desk to stand next to his chair, Noctis already expects it.

 

“You’re a man of mixed signals, you know,” Prompto huffs, the evil little menace that he is, his expression shifting to a pout now. He’s wiggling his hips, though, a hand sliding down his chest - down that soft, _worn,_ fabric - to hook under the band of his pants. His sweater hikes up, and Noct’s fingers grip tightly into the armrest of his chair as his eyes greedily take in that revealed stretch of delicious, freckle-dusted skin, well-earned muscle lean and shifting in smooth lines.

 

“Am I?” Noctis says quietly, a bit belatedly. It’s obvious who the star of this show is. Prompto Argentum, damn him, knows how hard it is for Noctis to resist him. He’d put up a good fight, but--oh, his self-control is dissipating, and rapidly.

 

“Uh-huh,” Prompto replies, though he’s starting to sound breathless. His fingers dig into the band of his pants even more, giving an evil little _tug,_ and oh, down they go, revealing the delicious jut of hipbone, the gorgeous lines of his pelvis, the trail of barely-visible, soft blonde hair, and _finally,_ down enough that his aching cock springs free of its confines.

 

Noct’s hand slides from its place on the armrest of his chair to press over the bulge in his pants, as his eyes greedily take in the sight of the boy, all worked up and desperate already. He’s so _cute_ like this, his cock wet at the tip. Prompto doesn’t stop, smoothly working his pants down over thighs that are still just slightly soft from the weight he’d previously carried. He only pauses to toe out of his shoes, and _then,_ when he straightens again, kicking his pants away, he _turns._

 

Noctis knows it’s coming, but he still can’t muffle the pleased sound he makes when Prompto shows off the plump curve of his ass, the smooth cheeks - with a few stray freckles, even there - round and perfect, and centered between, there’s a cute little jewel ( _a deep, forest green, a show of possession)_ peeking out, just visible. Noctis fucking hates the things this boy does to him.

 

“Told ya I was playing with my toy,” Prompto breathes out, and he barely gets the words out, before Noctis is _moving._

 

It all happens quickly. Noctis pushes his chair back, leans forward enough to get an arm curled around Prompto’s waist, and he tugs him _backwards,_ until Prompto’s falling back, sprawling heavily in his lap. There’s a quiet, mostly muffled sound of surprise, but Prompto sure as hell isn’t complaining. The force of being forced down in Noct’s lap slides the plug _deeper,_ and there’s a desperate, needy moan that follows.

 

The boy’s sounds are swallowed, though, by needy lips pressed to his. The kiss is messy, the angle awkward, Prompto’s neck craned to the side and Noctis leaning forward, but hands tangle in the boy’s hair, holding him there. Any of Noct’s tightly wound self-control is unravelling, because Prompto’s weight is settled directly over his aching cock. He can _feel_ the unyielding weight of the plug as it shifts in the boy’s ass, and Prompto tastes amazing. He was the boy’s first kiss - the _only_ one he’s ever kissed - and Prompto was a quick, wicked learner, as he is with everything.

 

Teeth drag into Noct’s lower lip, and he gives Prompto’s soft inner thigh a rough _squeeze_ in response. It earns him a moan, the vibration hot and needy against his lips. When they part, there’s saliva stringing between their lips, and Noctis finds the sense - momentarily, at least - to mutter a quiet silencing spell. It’s late, but sometimes staff roams the castle, and there’s always the threat of wandering students out of bed--like the one that’s hot and needy in his lap, after all.

 

“You gotta,” Prompto gasps, as a hand falls to grip at the side of Noct’s thigh, the boy leaning back to settle firmly against his chest, “teach me how to do that some day.”

 

Noctis laughs - because all he can do is _laugh,_ some things are too much to talk about, even to the boy he trusts most in the world - and steals another kiss instead. “Maybe,” he agrees, but his body has a very different idea at the moment. His hips are lifting up out of the chair, the thick weight of his erection pressing against the swell of Prompto’s ass, and they _both_ groan.

 

They shouldn’t do this, Noctis knows it. But god, he’s thrusting up, and Prompto, the little brat, is grinding back down against him with as much momentum as he can. The hand settled on Noct’s thigh steadies him, and with every thrust, it’s nudging the plug deeper into him, pressing into all his secret, sensitive places.

 

“ _Noct,”_ Prompto gasps, “ _Noctis,_ please. Fuck me, gods, _please,_ I need it, I want it--”

 

They go through this every damn time. It’s the _one_ line Noctis won’t cross, though his cock throbs angrily at the thought of it. It’d be so easy to reach between them, to pull that thick plug out. Prompto’s already stretched wide and open and pliant, all for him, he could unbutton his pants--could throw the boy over his desk, or just take him like this, riding his lap. Noct’s had so many dreams about it, he’s wanted it so badly--

 

“You _know_ we can’t,” he groans instead. Prompto whines, and bucks down harder on his trapped cock, but the protest dies on his lips when instead, the man’s hand shifts from his inner thigh to curl around his cock, fisting it roughly, base-to-tip, thumb swiping over the leaking slit.

 

They’re making a total mess. Prompto’s still half-dressed, his oversized sweater hiked up over his belly. The added friction of Noct’s pants is driving him insane, and he’s sure that there’s a wet patch where the tip is dripping heavily. He manhandles Prompto expertly, shifting and lifting him so that the plug’s driving directly into the boy’s prostate - but it’s not enough, _never_ enough. Prompto’s so hot, his skin burning up, and when he gets like this, Noctis worries that maybe he’ll combust on the spot. Or, hell, maybe he’ll simply blink from existence, a creature too perfect to exist in this world, the missing half of Noct’s life that he’s been looking for all along.

 

“ _Please,”_ Prompto gasps, instead. He twists in Noct’s grasp, free arm reaching back to hook around the man’s neck, fingers tangling in his hair. Their lips come together again, and Noctis can’t resist. Sometimes, he really _does_ try. More often - he takes control, rough and needy, and he makes Prompto beg and gasp and dissolve into a creature of sheer, utter need before he satisfies him.

 

But oh, he’s kissing Prompto, and Noctis _loves_ him. He hates how much he loves him. His hand’s working between the boy’s thighs, feeling the full weight of his cock, burning hot, hard and throbbing. There’s so much precome smoothing his strokes, and every time Noctis swipes over the tip, Prompto’s thighs outright _convulse._ He’s practically bouncing Prompto in his lap, his trapped cock grinding into the cleft of his ass, and he _wants_ to feel that tight heat wrapped around him, wants to take Prompto, to be his _first,_ his only, his everything--

 

Prompto’s orgasm takes Noctis by surprise. The boy breaks away, a desperate, needy cry escaping his lips - Noct’s thankful, yet again, for the hastily-cast silencing spell blanketing his office - as he jerks, full-bodied and desperate, his release spurting messy over Noct’s fingers. He’s trembling violently, the plug stil deep inside, still pressing into oversensitive nerves as he rides his release, as Noctis keeps grinding up, keeps pretending that he’s fucking him into oblivion--

 

“Noct, _please, please,_ fuck, I need it,” Prompto gasps through his orgasm, because Noctis is still touching him, is still jerking his cock even as he starts to soften slightly, even as his release drips down his inner thighs. Despite how pliant he is, soft and relaxed and perfectly overstimulated, Prompto keeps grinding down on Noct’s erection, keeps drawing him deeper into oblivion, into _perfection._

 

It’s blissful, and it doesn’t take Noctis long. It’d be embarrassing - a grown man coming so quickly, and in his pants - if it wasn’t _Prompto,_ if this boy wasn’t so fucking perfect and wonderful and pulled directly from his dreams. Noctis shudders, his teeth sinking into Prompto’s shoulder, biting down through the fabric of his sweater, as his hips jerk and stutter, as the wetness spreads over his pants. He doesn’t stop moving, doesn’t stop shifting Prompto’s smaller body until the euphoric bliss is too much, until they’re both panting, desperate, sweaty and messy and absolutely ruined.

 

“... mmm,” Prompto hums, softly, as he leans back into Noct’s strong chest. It’s pathetic, really, how much this boy has become the center of Noct’s world. Their bodies slot together perfectly, and Noctis shifts, slowly, a hand slipping up under the hem of Prompto’s shirt to stroke over the flat plane of his belly.

 

“... you’re a brat. I’m a mess,” Noctis laughs quietly. His hands are messy, covered in the remnants of Prompto’s release, smearing it over the boy’s already sweat-slicked skin. The touch is idle, reverent, more affection than anything else, and he can tell Prompto’s thriving in the simple contact, with how he writhes a little, giggling ever-so-slightly as he leans back further into the man’s chest.

 

“Wanted to make you feel good,” Prompto sighs, head tipping to the side so he can nuzzle into the scruff of Noct’s beard. “... I miss you. I hate being in the common room alone. Want to sleep in _your_ bed.”

 

Noctis sighs. They’ve had this discussion before. They’re always having _discussions,_ ones where Noctis reminds Prompto that he’s his professor, that Prompto’s _too young_ for this. He’d lose his job. More than that--it’d be a scandal. His father’s career could be ruined, his _own_ future career (as much as he doesn’t want it) would be prematurely destroyed, and… fuck, more than any of that, Noctis doesn’t want to smear Prompto’s reputation before it even begins. He won’t kill this kid’s chance at success. Not when he cares so much.

 

“Once you graduate,” Noctis promises, and it’s a promise he’s made before, time and time again. “I mean it, Prompto. You _know_ I’m sticking to this one.”

 

Prompto knows. Still, he’s nuzzling into Noct’s beard, pressing tiny kisses along the curve of his jaw, and it makes the man smile, makes his heart thump and his chest swell and everything feels warm and perfect. “... you’ve let me sleep in your bed before, though,” he points out quietly. “We could just _sleep._ I’ll get up before anyone else wakes up, promise, and be back in bed before anyone knows I’m gone…”

 

Every time they have _this_ discussion, too, Noctis tries to stick his ground. He can’t resist some things, though, and having Prompto Argentum in his arms, warm and content, is one of them. Noctis doesn’t sleep well without him - he sleeps long and often, but never sound and _deeply,_ not unless he’s curled around the smaller body of this ridiculous boy - and he sorely hates having an empty bed, even as he tries to be the noble one.

 

“Prom…” he starts to say, but Prompto surges forward anyway, after stealing another kiss, rough and breathless and absolutely _mindless_ with love and affection.

 

“I need a shower, Noct,” Prompto points out, “and I can’t exactly go back to the Puff common room smelling like sex. What if someone _sees_ me sneaking a shower at midnight…”

 

That’s not a new argument, either, and it’s always the winning one. It’s easier to justify, after all, if Prompto has a real, solid excuse.

 

“... just for tonight,” he relents, finally, sighing. “... you’re a brat, Prompto. I’m gonna pick on you in class tomorrow.”

 

Prompto laughs, though, and he twists a little more - groaning because that cursed plug is still buried deep inside of him - to steal another kiss, this one lingering longer, but softer, all gentle presses of lips and chased with tiny pecks and licks. “Don’t you always, _sir?”_

 

Noctis shudders and groans, and in his ruined pants, his cock’s twitching again. “Don’t tempt fate, Argentum,” he teases, but they both know that Prompto’s absolutely asking for it. And, hell, if he’s already fallen this deeply tonight, what’s a little more? “You’ll be in for some _real_ punishment.”

 

“Yeah?” Prompto breathes out, and Noctis recognizes the hint of _hopefulness_ in his tone. Prompto is relentless, and he’s insatiable, and the combination is absolutely deadly. “Dunno. Sounds like a lot of talk, Noct, and absolutely no action.”

 

Noctis sucks in a breath, and he grips at Prompto’s thigh, sudden and rough. His lips find the boy’s throat, sucking at the delicious column of smooth, pale skin, and the needy _moan_ it pulls from Prompto’s lips is absolutely perfect. If he’s this deep in hell, he might as well fully indulge and enjoy after all, right? And the night, for them, is apparently just beginning.

 

\----

**Author's Note:**

> THANKS IF YOU READ THIS LMAO.
> 
> i have actual plot-centric fic written for this AU, so if you wanna read it, please let me know! <3 <3 i fully expect everyone to side-eye my gross harry potter AU shit anyway. 
> 
> (and yes, noct was a slytherin when he was in school, FITE ME, prompto's a perfect little puff boy, AND I HAVE SO MANY FUCKING FEELS FOR THIS AU VERSE I LOVE IT SO MUCH ALSDJFLSDFJ)
> 
> you can scream at me on twitter @thatdest. SO MUCH CREDIT GOES TO MY FRIENDS ON AO3, Overlimits and Krityan for creating this AU with me, all the lore/headcanons belong to them as well! <3


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